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If the starter motor turns normally but the engine does not fire, one of the three elements of combustion is missing: fuel, spark (or hot compression on diesels) or the go-ahead from the ECU.

What to observe

• Does the dashboard come on normally? Do the lights go out?
• Is the immobiliser light flashing?
• Can you hear the fuel pump hum when the ignition is switched on?
• Is the problem only when cold, only when hot, or always?

Most common causes

• Faulty crankshaft (or camshaft) sensor: the classic cause of a no-start
• Fuel pump or relay fault
• Immobiliser not recognising the key
• Clogged diesel filter or air in the circuit
• Weak glow plugs on cold diesels
• Coils or spark plugs on petrol engines
• Timing out of phase (belt or chain)

What to do right away

• Do not keep cranking for long: you risk flattening the battery and flooding the engine
• Try the spare key: it rules out the immobiliser
• Have the faults and the crank sensor signal read while cranking

How MasterTuning helps

We do not replace parts by trial and error: we read the real values from the ECU (pressures, flow rates, corrections, temperatures) and identify the component responsible. Then we repair and recalibrate the software where needed. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · find an installer

Does your car have this symptom? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

Why does the car not start when cold but does when warm?

On diesels it is typical of weak glow plugs or preheating; on petrol engines it can depend on temperature sensors or fuel pressure.

The immobiliser light is flashing: what does it mean?

The ECU does not recognise the key transponder and blocks injection. Try the spare key and have the anti-theft system checked.

Can the crank sensor prevent starting?

Yes: without a crankshaft position signal the ECU does not control injection and ignition.